Safety lock for extensible masts



May 23, 1950 9.J MOON AL 2,508,835

v SAFETY LOOK FOR EXTENSIBLE MASTS Filed June 15, 1946 3 Sheets-Sheet l v I N VENTORQ JAMES Moo/v ahd Ila/INF H W \By May 23, 1950 J. MOON El AL 2,508,835

SAFE'I'Y LOCK FOR EXTENSIBLE MASTS Filed June 15, 1946 3 Sheets-Sheet 2 INVENTOR. JAMES MOON and (foul/15140 w 1.2 TTOR/VE y.

May 23, 1950 J. MO'ON ET AL 2,508,835

SAFETY LOCK FOR EXTENSIBLE MASTS Filed June 15, 1945 s Shets-$heet s INVENTORS, JAME Moo/v ATTORNEY.

Patented in, 2a, 1950 SAFETY LOOK FOR EXTENSIBLE MASTS James Moon and John F. Shaw, Altadena, calm, as'signors to Western Oil Tool & Engineering Co. Inc., Glendale, Calif., a corporation of Call fornla Application June 15, 1916, Serial No. 677,031

This invention relates to a safety device for a sectional derrick or ladder, mast, or other structure to be erected for purposes of carrying a load to such a structure.

It is quite common to employ such structure in sectional form, one section being adapted to be elevated and carried upon a lower section to vary the height of the structure. It is also common to provide a, locking means to hold the elevated section in position on the lower supporting section.

Examples of such structure may be found in the telescoping, portable derrick or mast employed in drilling of oil wells and in operations around producing wells.

Such structures are such as are illustrated in United States Patents Nos. 2,204,713; 2,358,715; and 2,336,432. In such structures the mast is composed of a lower portion which is hinged or otherwise mounted on the vehicle on which .it is transported. It may thereafter be erected in an upright position and lowered therefrom onto the vehicle. The upper portion is telescoped within the lower portion when the derrick or mast is in position on the vehicle. After the lower portion is erected, the telescoped upper portion is raised and extended by means of a line which causes the extension of the mast. This line passes over a reel which applies the power for lifting or lowering the upper portion of the derrick or mast. When the derrick or mast is fully extended, various locking means may be employed to hold the derrick or mast in the extended position.

It is not an uncommon experience that the hoisting or elevating line parts or some accident occurs either during the lifting or lowering of the telescoping section when the power goes oif or the winch or reel breaks down. The telescoping portion then falls, causing great damage and resulting, in numerous cases, in serious injury to operating personnel.

We have designed and built a safety lock or catch which, whenever slack occurs in the line or the line breaks in such circumstances as to permit the telescoping portion to fall and before such fall occurs, locks the derrick in place. The safety lock of this invention may operate at any position of the telescoping section during its extension or at the limit of extension or during retraction. Our locking mechanism wfll operate to hold the derrick at any attained position whenever slack on the hoisting line or a, break therein occurs, which, except for the presence of our locking device, would cause the telescoping section to fall.

4 Claims. (Cl. 254- 148) These objects and others will be clear to those skilled in the art from a further description of our invention taken together with the drawings.

.in which line, showing the arrangement of the sheaves;

Fig. 4 is a section taken on the line 4-4 of 8. 2;

Fig. 5 is a detail in part section showing the switch mechanism;

Fig. 6 is a view taken on' line 68 of Fig. 5;

Fig. 7 is a, detail showing in part section the wedge lock and showing also schematically the wiring diagram and the switch;

Fig. 8 is a section taken on line 8-8 of Fig. '7; and

Fig. 9 is a view taken on line 9-9 of Fig. 7.

The telescoping derrick or mast is composed of a lower section i in which telescopes the upper section 3. The lower section I is mounted on the truck 2 so that it may,'when section 3 is lowered, rest on truck 2, and is lowered onto the truck by pivoting section i on a pivot mounting not shown in the drawing. The elevating mechanism and other conventional equipment usually mounted on the truck are omitted for clarity, since they do not form part of this invention.

When the derrick is moved to an upright position, it is securely locked in said upright position, as shown in Figs. 1 and 2. The telesoping portion 3 (see Figs. 1, 2, and 4, inclusive) slides inside the lower section I with the longitudinal posts 4, 6, or 3 sliding in guides 5 and I mounted on I.

In order to lift and lower the telescoping section 3, a cable 8, passing over power reel 9 and sheave i0 mounted on the truck 2, is threaded over sheave H mounted on the lower section of l and over sheave l2 mounted on the top brace 30 of l and over sheaves l3 and I4 mounted on the lower part of the telescoping section of 3 and to a deadhead I5 mounted on the top brace 30.

When the line is shortened by winding it upon the reel 9, the section 3 is raised to extend the length of the derrick, and when the line is unreeled the telescoping section descends. Should the line 8 part or should a winch failure or power shut-oi! occur during the raising orlowering of 3 3, it will drop, and since it is quite heavy damage or injury may occur. 4

In order to provide against this eventuality, we have devised a safety catch or lock which will hold the upper section in any position attained by the derrick during lifting or during lowering and will also look the upper section in position. This will prevent the upper section from dropping when slack occurs in the line either due to the parting of the line or any failure in the hoisting mechanism during lifting or lowering.

As will be recognized, during lowering and extending operations, the line 8 is under tension. We have designed a latch or lock arrangement which engages one or moreof the upright leg members of the telescoping section and which look sets to lock such leg member to the lower section when slack occurs in the line, but which remains in open position to permit the free movement of the upper section so long as tension is maintained on said line.

We accomplish this function by mounting upon the lower member I a switch mechanism which is operated to open a circuit whenever slack occurs in the line. When the switch is operated to open the circuit, slips mounted on I are set to engage the legs of the section 3 to lock the legs of 3 to the section I.

Such a switch is illustrated inFigs. 5 and 6.

It is composed of a casing I6 in which is mounted a quick-acting switch I1 of which many forms are available on the market, as will be understood by those skilled in this art. The switch is operated by a shaft I8 which is actuated by an arm I! acting against a spring 20. The rod 22 is pivotally connected to I9 at 2| and may be reciprocated in a bore 23a in the casing I6. Adjusting screws 24, 25, and 23 are provided; The rod 22 is lifted by arm 26 against spring 21 when the arm 23 is moved to the left and spring 21 returns the rod 26 to move the rod 22 downward when the arm 28 moves to the right. When the rod 22 is lifted the arm I9 moves the switch to closed position, and when the rod 22 moves downward the switch is opened. By adjusting nuts 24 and 25, some lost motion of desired amount is permitted in 26 before actuation of the rod I 9 occurs.

The switch mechanism It is mounted on the lower section I, at some convenient place, suitably between sheaves II and I2 so that the roller bears against the line 8 when the line is in tension. The roller 28 is set against the line so as to raise 28 to place the switch I1 in closed position. The nuts 25 and 24 are adjusted so that the vibration of the line 8 during operation will not trip the switch I1. The motion of arms 28 which will trip the switch, as determined by the settings of 23 and 25, is therefore something in excess of that vibrating movement of 8.

This occurs when slack appears in line 8 or it parts. Then the spring 21 snaps the rod 22 downward to trip the switch.

The tripping of the switch opens a circuit which permits the safety catch to operate. This catch or lock 3| is mounted upon the brace 38 (see Figs. 1 and 2), which is cut out at 32a to fit the curvature of the leg Ii of section 3. The latch consists of a base 32 upon which is mounted a housing 3| and side members 38. The walls 38 are stepped at 38. On steps 39 is mounted a plate 43 having an arcuate portion 4| to fit the curvature of the tubular leg 6 of section 3. The face of the housing 3| is covered by an inclined plate 33 which carries a cut-out slot 31. Within the housing chamber 38 of the housing 31, and mounted on the plate 33, is a pair of electromag- 4 netic solenoids 34 and 33 connected in parallel.

The armatures of the solenoid are connected to an arm 33 which passes through the slot 31. The rod 43 is screwed into the arm 36 and carries a washer l5, and passes slidably through an appropriate bore 32 of the plate 40. A spring 43 is mounted between the plate 4| and the washer 45. A plurality of wedge dies III having an arcuate face to engage the tubular leg 8 are slidably mounted on the wedge 33 which has an arcuate face to accommodate the arcuate steps 50 and a plane back to conform with the face 33. The wedge 49 is mounted on bolt 41 which passes through a bore 46 in the arm 36 and operates against the spring 38.

When the line is in tension the switch is closed to complete the circuit through the solenoids. This causes the armatures to lift arm 36 and wedge is against the springs 43 and 48 to move the wedges up the inclined plane of 33 to free the slips 5 from the leg 6 which is then free to move. Should slack or failure of the line 8 cause the switch to operate to open the circuit through the solenoids 34 and 35, the springs 44 and 48 will act to snap the wedge 43 downward down the inclined plane 33 to set the slips 50 against the leg 6 to lock the legs and therefore the section 3 at any attained position, as explained above.

It is to be noted that since this safety measure is desired primarily to function during the limited times that the section 3 is extended or retracted, the switch It is set to keep the circuit through the solenoids open until a tension is exerted on the line when the circuit is closed to unlock the wedge lock. When the accident occurs, and against which it is intended to guard, i. e., when slack occurs, the circuit is opened and the wedges set.

While we have described a particular embodiment of our invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

We claim as our invention:

1. A safety latching means for a sectional extensible mast comprising a lower mast portion and an upper mast portion, said upper mast portion being carried upon said lower mast portion and extensible or retractible on said lower mast portion by a hoist line, a latch including a base mounted upon said lower portion, an inclined plate mounted on said base, a wedge slidably mounted on said plate, a solenoid, an arm connecting the armature of said solenoid with said wedge, a spring mounted on said arm to oppose the motion of said wedge when the solenoid is energized and to move the wedge in opposite direction when the solenoid is de-energized, a power circuit connected to said solenoid, a switch in said power circuit, said switch being mounted in proximity to said hoist line, said switch including an arm bearing against said line when said line is in tension, a switching mechanism operated by the motion of said arm to control the operation of said solenoid.

2. A safety device for an extensible mast comprising a mast formed of an outer and an inner extensible section, the inner section telescoping into the outer section, means for extending said mast comprising a hoist line connected at one end of said line to the top of said outer section and to ahoist at the other end of said line, a sheave mounted on the lower end of said inner section, said line passing over said sheave whereattachment of said line to the top of said outer section and to said hoist.

3. A safety device for an extensible mast comprising a lower mast section, said lower mast section being composed of upright legs and top and intermediate cross braces, an extensible mast section, said extensible mast section being composed of upright legs and braces therefor, said extensible mast section being adapted to slide over said lower portion during extension or retraction of said extensible mast section, the legs of said lower section being contiguous to complementary legs of said lower portion, a hoist line passing through said mast and connected to an upper brace oi said lower portion and to a lower brace of said extensible section and to a hoist, means for extension or retraction of said extensible mast section, a latch mounted on an upper cross brace of said lower portion of said mast to lock the legs of said extensible section to said lower portion, means operatively connected at an intermediate point of said line between said point of connection oi said line to the outer section and said hoist for maintaining said latch open when said line is in'tension during 6 said extension and lowering, said means also setting said latch to lock said sections together on appearance of slack in said line.

4. A latch for a sectional, extensible mast, said latch comprising an inclined plate, a wedge slidably mounted on said plate, a solenoid, an arm connected to the armature oi! said solenoid connecting the armature 01' said solenoid with said wedge, a spring mounted on said arm to oppose the motion of said wedge when said solenoid is energized and to move said wedge in an opposite direction when the solenoid is de-energized, a power circuit connected to said solenoid, a switch in said power circuit, said switch being adapted to be mounted in proximity to a hoist line for extension of said mast, said switch including an arm adapted to bear against such hoist line when said hoist line is in tension, a switching mechanism operated by the motion of said am to control the operation of said solenoid.

JAMES MOON. JOEI F. SHAW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 293,851 De Castro Feb. 19, 1884 740,942 Stevenson Oct. 6, 1903 837,253 Secoy Nov. 27, 1906 1,260,216 Lepley -1--- Mar. 19, 1918 1,644,613 Royer Oct. 4, 192'! 2,204,713 White, Jr. June 18, 1940 2,331,558 McEwen et al Oct. 12, 1943 

